when doing a select by area with shift pressed the object under the mouse will not be unselected if it was already selected (xctx->already_selected)

src/callback.c

@@ -1260,7 +1260,7 @@ int rstate; /* (reduced state, without ShiftMask) */
     }
 
     redraw_w_a_l_r_p_rubbers();
-    /* start of a mouse area select */
+    /* start of a mouse area select. No shift pressed */
     if(!(xctx->ui_state & STARTPOLYGON) && (state&Button1Mask) && !(xctx->ui_state & STARTWIRE) && 
        !(xctx->ui_state & STARTPAN) && !(SET_MODMASK) &&
        !(state & ShiftMask) && !(xctx->ui_state & (PLACE_SYMBOL | PLACE_TEXT)))
@@ -1280,6 +1280,7 @@ int rstate; /* (reduced state, without ShiftMask) */
         }
       }
     }
+    /* Unselect by area */
     if((state & Button1Mask)  && (SET_MODMASK) && !(state & ShiftMask) &&
        !(xctx->ui_state & STARTPAN) && 
        !(xctx->ui_state & (PLACE_SYMBOL | PLACE_TEXT))) { /* unselect area */
@@ -1287,6 +1288,7 @@ int rstate; /* (reduced state, without ShiftMask) */
         select_rect(START,0);
       }
     }
+    /* Select by area. Shift pressed */
     else if((state&Button1Mask) && (state & ShiftMask) &&
              !(xctx->ui_state & (PLACE_SYMBOL | PLACE_TEXT)) &&
              !(xctx->ui_state & STARTPAN) ) {
@@ -1296,8 +1298,10 @@ int rstate; /* (reduced state, without ShiftMask) */
         }
         if(abs(mx-xctx->mx_save) > 8 || 
            abs(my-xctx->my_save) > 8 ) {  /* set reasonable threshold before unsel */
-          select_object(X_TO_XSCHEM(xctx->mx_save),
+          if(!xctx->already_selected) {
-                        Y_TO_XSCHEM(xctx->my_save), 0, 0); /* remove near obj if dragging */
+            select_object(X_TO_XSCHEM(xctx->mx_save),
+                          Y_TO_XSCHEM(xctx->my_save), 0, 0); /* remove near obj if dragging */
+          }
           rebuild_selected_array();
         }
       }
@@ -2714,17 +2718,12 @@ int rstate; /* (reduced state, without ShiftMask) */
     xctx->yorigin-=-CADMOVESTEP*xctx->zoom/2.;
     draw();
    }
+   /* Alt - Button1 click to unselect */
    else if(button==Button1 && (SET_MODMASK) ) {
      xctx->last_command = 0;
      xctx->mx_save = mx; xctx->my_save = my;
      xctx->mx_double_save=xctx->mousex_snap;
      xctx->my_double_save=xctx->mousey_snap;
-
-     /* useless code ? 20200905 */
-     /* if(xctx->semaphore<2) {
-       rebuild_selected_array();
-     } */
-
      select_object(xctx->mousex, xctx->mousey, 0, 0);
      rebuild_selected_array(); /* sets or clears xctx->ui_state SELECTION flag */
    }
@@ -2902,6 +2901,7 @@ int rstate; /* (reduced state, without ShiftMask) */
        tcleval("set constrained_move 0" );
        break;
      }
+     /* Button1Press to select objects */
      if( !(xctx->ui_state & STARTSELECT) && !(xctx->ui_state & STARTWIRE) && !(xctx->ui_state & STARTLINE)  ) {
        Selected sel;
        int prev_last_sel = xctx->lastsel;

src/select.c

@@ -1224,31 +1224,38 @@ void select_line(int c, int i, unsigned short select_mode, int fast )
 Selected select_object(double mx,double my, unsigned short select_mode, int override_lock)
 {
    Selected sel;
+   xctx->already_selected = 0;
    sel = find_closest_obj(mx, my, override_lock);
-
    dbg(1, "select_object(): sel.n=%d, sel.col=%d, sel.type=%d\n", sel.n, sel.col, sel.type);
 
    switch(sel.type)
    {
     case WIRE:
+     if(xctx->wire[sel.n].sel) xctx->already_selected = 1;
      select_wire(sel.n, select_mode, 0);
      break;
     case xTEXT:
+     if(xctx->text[sel.n].sel) xctx->already_selected = 1;
      select_text(sel.n, select_mode, 0);
      break;
     case LINE:
+     if(xctx->line[sel.col][sel.n].sel) xctx->already_selected = 1;
      select_line(sel.col, sel.n, select_mode,0);
      break;
     case POLYGON:
+     if(xctx->poly[sel.col][sel.n].sel) xctx->already_selected = 1;
      select_polygon(sel.col, sel.n, select_mode,0);
      break;
     case xRECT:
+     if(xctx->rect[sel.col][sel.n].sel) xctx->already_selected = 1;
      select_box(sel.col,sel.n, select_mode,0, override_lock);
      break;
     case ARC:
+     if(xctx->arc[sel.col][sel.n].sel) xctx->already_selected = 1;
      select_arc(sel.col,sel.n, select_mode,0);
      break;
     case ELEMENT:
+     if(xctx->inst[sel.n].sel) xctx->already_selected = 1;
      select_element(sel.n,select_mode,0, override_lock);
      break;
     default:

src/xinit.c

@@ -613,6 +613,7 @@ static void alloc_xschem_data(const char *top_path, const char *win_path)
   xctx->only_probes = 0;
   xctx->menu_removed = 0; /* fullscreen previous setting */
   xctx->save_lw = 0.0;  /* used to save linewidth when selecting 'only_probes' view */
+  xctx->already_selected = 0;
   xctx->onetime = 0; /* callback() static var */
   xctx->save_netlist_type = 0;
   xctx->some_nets_added = 0;

src/xschem.h

@@ -972,6 +972,7 @@ typedef struct {
   int *node_mult;
   int node_mult_size;
   /* callback.c */
+  int already_selected; /* when clicking on an object that is already selected this will be 1 */
   int mx_save, my_save, last_command;
   char sel_or_clip[PATH_MAX];
   int onetime;